Measuring 250 miles (400 km) wide, the now-buried crater in Australia was ground zero for a cataclysmic impact that occurred some 300 million years ago. But is it really the largest on Earth?

According to a new study published in the geology journal Tectonophysics, the asteroid broke into two before it struck the ground. When the objects hit the Warburton West Basin, each fragment measured more than six miles (10 km) across.

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Today, the impact crater can no longer be seen. But by modeling the geophysical structure below the surface, the Australian National University scientists were able to isolate signs of two massive impacts. The researchers also found geophysical anomalies and quartz deformation in the samples pulled from drill cores. Some of the rock, for example, had turned to glass — a phenomenon consistent with a massive impact.

Image: Glikson et al.

"It would have been curtains for many life species on the planet at the time," lead researcher Andrew Glikson told the BBC.

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That said, no evidence has been found to link it to any particular mass extinction. As noted in the BBC article, "The rocks around the impact zone are roughly 300 to 600 million years old, but a layer of ash that would have been thrown up by the impact has not been detected as sediment in rock layers from the same period."

Interestingly, the site of the crash was discovered by accident as the scientists were drilling for a geothermal research project.